The Control Of Construction Deformation And The Analysis Of Stability About Large Section Tunnel With Bias And Weak Rock

With the building of a large mountain tunnel traffic, bias weak rock deformationcontrol of construction and its stability problem has become the key research contentof tunnel engineering in recent years. The background of this paper is Liu JiaZhuangtunnel of the Shanghai-Kunming passenger dedicated line. By using the finite elementsoftware of ABAQUS, analysis the construction process about the large section tunnelof bias soft rock, and compared the three kinds of different excavation scheme,research and analysis the change rule of surrounding rock and supporting structurestress and strain. Using the grey control equation, the stability of surrounding rock isjudged according to the monitoring measure, and put forward some constructiondeformation control measures. The main content of researching are as follows:(1)During the process of the ABAQUS simulating on tunnel construction, thearch foot of the primary supporting structure produce the stress concentration after thefirst step of excavation and supporting, and produce significant extrusion deformationat the bottom of the upper section, and produce the area of stress release at the top ofthe vault; After the second step of excavation and supporting, there appears stressconcentration in the wall and arch foot, and produce the area of stress release at thebottom of the vault, but there are no change at the top of the vault. During the wholeprocess of tunnel construction, the maximum stress of`the primary supportingstructure occurs in the sidewall and arch foot supporting structure, the minimum stressof the primary supporting structure occurs in the bottom of the stairs. The stressinfluence range of the cavern surrounding is (6~20)m. The displacement of horizontal is larger at the waist and arch tunnel arch foot, the largest vertical displacement in thevault.(2)Compared with three methods of construction：①When use the full faceexcavation method, the displacement of rock around is maximum, and the stress isminimum, the maximum stress is the value of0.37times for CD excavation method. Ifallowed larger deformation, the full face excavation method can be used in engineeringconstruction.②When using the method of benching tunneling method, it can be goodto control the deformation of the building, the maximum displacement is the value of0.57times for full face excavation method, the maximum stress is the value of0.39times for CD excavation method.③When use CD method, the displacement of rockaround is the minimum, and the stress is maximum, maximum displacement is thevalue of0.46times for the full face excavation method, and is the value of0.75timesfor the maximum of benching tunneling method. When the span of the tunnel is verybig, the surface subsidence is strict, the conditions of surrounding rock is particularlypoor, and benching tunneling method is difficult to control the deformation of thesurrounding rock, CD method can be used.(3)Put forward the grey control equation based on the linear combination model:predict the vault subsidence, horizontal convergence and the inverted archsedimentation of the D1K923+730section, the value of grey control equation were79.2mm,9.2mm and20.9mm; Through the monitoring measurement, the measuredvalues of this section were74.3mm,9.2mm and18.6mm; The predicted values andmeasured values are basically identical, the displacement of surrounding rock can beaccurately predicted by using grey control equation. Through the organic combinationof the grey rate equation and the grey displacement equation, it can accurately judgethe stability of surrounding rock and ensure the safety of the construction.(4)When tunnel become stability, the vault subsidence, horizontal convergenceand inverted arch subsidence of the Liu JiaZhuang tunnel are85mm,15mm and35mm,stable time is45days. In construction of information dynamic, they can berespectively as the limit value of the displacement when use the grey controllingequation of the tunnel. Judge the stability of surrounding rock, the tunnel of passingthrough the coal seam is in danger, suggest immediately strengthen the structure of the supporting or change the way of the excavation to control the stability of surroundingrock.